LAHORE/MULTAN, Pakistan, Aug 10 (Reuters) - Dissident cleric Tahir ul-Qadri who aims to topple Pakistan's government announced on Sunday that his followers would stage a demonstration in the capital on Thursday, on the same day as an opposition protest led by Imran Khan.

The announcement is likely to unnerve the ruling party. Some in the government suspect the protests are backed by individuals within the military as a way of weakening the civilian government and discouraging it from pursuing policies the military disapproves of.

The nuclear-armed country of 180 million has a history of coups, protests and violent political rivalry though the military denies meddling in politics.

"Our revolution march will start on August 14 and will go parallel to the freedom march of Imran Khan," Qadri said in a televised address on Sunday. "If I am assassinated, don't leave (Prime Minister Nawaz) Sharif and his cabinet members alive."

Police registered a murder case against Qadri on Sunday after three policemen were killed in clashes with his supporters.

"Qadri is responsible for killing police officials and his own workers. Police have booked him for terrorism and murders and will arrest him soon," said Rana Mashhood Ahmad, the law minister of Punjab province, where the clashes between the clerics' supports and police erupted on Friday.

In Pakistan, police must register a case against someone before charging him with a crime.

A spokesman for Qadri said eight of his supporters were killed and more than 100 wounded in clashes with police over the past two days.

POLICY DIFFERENCES

On Sunday, hundreds of Qadri's supporters stood outside his house in the eastern city of Lahore reciting the Koran as a helicopter rattled overhead, apparently monitoring the crowd.

The spectre of tension between the civilian government and the military has arisen in particular because of the prosecution for treason of Pervez Musharraf, a former army chief who went on to become president.

Some in the army have privately criticised the legal action against their former boss, who as army chief in 1999 overthrew Nawaz Sharif when he held the office.

Sharif's government has also made improving relations with India a cornerstone of its policy. The military is believed to be less keen on such a move towards Pakistan's old enemy and nuclear-armed rival and sees external relations as its domain.

The government and the military have also disagreed on how to handle Pakistani militants fighting the state.

The weekend violence forced Qadri to change his plan for a mass protest in Lahore on Sunday. Instead, his supporters held protests in their own towns in memory of 14 supporters he said were killed by police in June. They had clashed with police over security barricades around Qadri's house.

Police say they have arrested more than 500 of Qadri's supporters over the past few days. They dragged many of them from their beds in the middle of the night, activists say.

A week ago, the government deployed the military to protect key installations in the capital. Officials said it was to protect against Taliban attacks but opposition leader Imran Khan says it is an attempt to intimidate protesters.

Khan is demanding electoral reforms and an investigation into last year's polls, which Sharif won in a landslide victory. (Writing by Katharine Houreld; Editing by Robert Birsel and Janet Lawrence)